Allow links at the OverlayPlot level

holoviews/core/dimension.py

@@ -557,8 +557,8 @@ def clone(self, data=None, shared_data=True, new_type=None, link=True,
 
         if data is None and shared_data:
             data = self.data
-            if link:
-                settings['plot_id'] = self._plot_id
+        if link: # HACK
+            settings['plot_id'] = self._plot_id
         # Apply name mangling for __ attribute
         pos_args = getattr(self, '_' + type(self).__name__ + '__pos_params', [])
         return clone_type(data, *args, **{k:v for k,v in settings.items()

holoviews/plotting/bokeh/links.py

@@ -85,7 +85,7 @@ def find_links(cls, root_plot):
         Traverses the supplied plot and searches for any Links on
         the plotted objects.
         """
-        plot_fn = lambda x: isinstance(x, GenericElementPlot) and not isinstance(x, GenericOverlayPlot)
+        plot_fn = lambda x: isinstance(x, (GenericElementPlot, GenericOverlayPlot))
         plots = root_plot.traverse(lambda x: x, [plot_fn])
         potentials = [cls.find_link(plot) for plot in plots]
         source_links = [p for p in potentials if p is not None]

holoviews/plotting/plot.py

@@ -994,7 +994,7 @@ def link_sources(self):
             zorders = [self.zorder]
 
         if isinstance(self, GenericOverlayPlot) and not self.batched:
-            sources = []
+            sources = [self.hmap.last]
         elif not self.static or isinstance(self.hmap, DynamicMap):
             sources = [o for i, inputs in self.stream_sources.items()
                        for o in inputs if i in zorders]